The present invention is generally in the area of medical catheters, and specifically to catheters constructed to facilitate guidance and placement of a distal end portion thereof at a predetermined site within the body of a patient.
A variety of methods for placing catheters and tubes in a patient's body are known. For example, enteral nutritional products can be delivered to a patient's gastrointestinal tract via a tube which is introduced through the naris of the patient's nose. The tube is advanced through the patient's esophagus and into the patient's stomach. In the event that it is preferable to deliver the enteral nutritional product directly to the patient's small bowel, the tube is further advanced beyond the pylorus into the patient's duodenum or small bowel. However, advancement of the tube into the patient's duodenum can be difficult in many patients. One method for advancing a tube through the stomach and into the duodenum entails the use of the natural peristaltic movement of the gastrointestinal tract. Such advancement may require as long as three to five days in some patients. Pharmaceutical products can be used in order to enhance the peristaltic action within the gastrointestinal tract and thereby decrease the time required to advance the feeding tube into the small bowel.
Serial X-rays typically are used to determine the location of the distal end of the tube as it advances by peristaltic action through the pylorus to the duodenum, thereby exposing the patient repeatedly to radiation and increasing the costs associated with placement of the tube. For these reasons, the use of naturally occurring or pharmaceutically enhanced peristalsis provides a sub-optimal method for placing a tube in a patient's small bowel.
It is known in the art to use magnetic flux or a magnetic field in the placement of catheters in the gastrointestinal tract. For example, U.S. Pat. No. 3,043,309 to McCarty describes the use of a localized magnetic field generated by an electrical magnet to manipulate a suction tube having a magnetic member at its distal end. The suction tube is constructed to be manipulated through an intestinal obstruction. The electrical magnet enables a medical professional to turn off the magnet when using fluoroscopy radiation to determine the precise location of the distal end of the tube. Without the ability to deactivate the magnetic field in this manner, the field would distort the image on the fluoroscopy screen, thereby preventing a precise determination of the location of the distal end of the tube.
U.S. Pat. No. 3,794,041 to Frei, et al. discloses beads of a ferromagnetic material constructed to be inserted in a body part with a catheter for moving the body part using an external magnet. U.S. Pat. No. 3,847,157 to Caillouette, et al. discloses the use of a magnetic indicator in a medico-surgical tube to identify the location of a tube containing a ferromagnetic material. U.S. Pat. No. 3,674,014 to Tillander discloses a distal end portion of a catheter having a plurality of magnetic tubular elements with ball-shaped ends to allow deflection of the sections with respect to each other for guidance of the catheter distal end. U.S. Pat. Nos. 3,961,632 and 4,077,412 to Moossun disclose a trans-abdominal stomach catheters of the Foley type used to direct the placement of the catheter by way of an external puncture from outside the abdomen through the stomach wall. U.S. Pat. No. 3,358,676 to Frei, et al. shows the use of magnets for remotely controlling propulsion of a magnet-containing beads through a duct of a human.
U.S. Pat. No. 5,431,640 to Gabriel discloses the use an external magnet to establish a magnetic field for permeating body tissue and enveloping the lesser curvature of the stomach for magnetic direction of a distal end of a catheter feeding tube having a permanent magnet associated therewith. The presence of the permanent magnet on the distal end portion of the catheter tube presents the advantage of steering the catheter magnet by the external magnet.
Maneuvering a catheter to the distal duodenum of a patient using the magnetic field produced by an external magnet requires precise knowledge of the anatomy of the stomach and duodenum in relation to the abdominal surface of a patient. This knowledge is necessary so that the operator can maneuver the external magnet over the abdomen of the patient in a precise path resulting in advancement of the catheter through the stomach and into the duodenum of the patient. An operator maneuvering an external magnet cannot see through the abdominal wall to decide whether the distal end portion of the catheter is continuously captured by the magnetic field of the external magnet during the advancement of the catheter. Thus, an additional procedure is required to determine whether the distal end of the catheter is properly advancing into the patient's duodenum. One method discussed previously and having apparent shortcomings involves the use of X-ray monitoring to confirm the position of the distal end of the catheter. An alternative method, described in U.S. Pat. No. 5,431,640, entails the aspiration of fluid from the distal end of the catheter and the measurement of the pH of the aspirated fluid. However, pH values for a particular individual may vary from expected values, as occasionally occurs in response to medications, thereby resulting in false position information. What is needed is an apparatus and method for advancing the distal end portion of a catheter using the field of an external magnet which provides an indication whether the catheter distal end is captured by the external magnet, thereby indicating whether the distal end of the catheter is being properly advanced into the patient's duodenum.
It is an object of the present invention to provide catheters which are more easily and accurately positioned than the catheters currently available.